- Adapt: organisms become better suited to environmental conditions via heritable (genetic) change over generations.
- There is a ying and yang between the environment and evolution
- complementary forces that interact to form a dynamic system
Evolution by natural selection
Evolution by natural selection
Natural Selection: Differences among individuals in a population in survival and reproduction
Organisms which are better suited to their environment survive and reproduce better, leading to a change in the average traits of a population over time
Evolution by natural selection
Natural Selection: Differences among individuals in a population in survival and reproduction
Fitness: Measure of ability to survive and reproduce
Adaption: A trait that confers an advantage in a particular environment that evolved via natural selection
What did Darwin mean by fitness?
- Best suited for the environment
- biggest? fastest? strongest? smartest?
- He intended “fittest” to mean the members of the species best suited for the immediate environment
- individual needs the most favorable traits to survive in the environment
- environments can change at any time
- Those lacking the favorable traits—the “unfit”—most likely won’t live long enough to pass down their unfavorable traits
- those traits will be breed out of the population
- ‘breeding out’ traits can take a long time
Conditions necessary for natural selection
-
Variation: Individuals in a population vary
- mutation as ultimate source of variation
- migration -> gene flow within species
- introgression -> genetics crosses species boundaries
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Heredity: Offspring resemble parents
- DNA as primary mechanism of heredity
- Differential survival or reproduction: Not all individuals survive, those with favorable traits survive and reproduce
Ways of studying adaptation (experimental evolution)
Ways of studying adaptation
Ways of studying adaptation
Advances in DNA sequencing
Advances in DNA sequencing
Advances in DNA sequencing
Advances in DNA sequencing
Advances in DNA sequencing
We can also now do genetic studies without harming any animals
Real world example: reivisting the white sands
Evolution by natural selection
The dunes are a dramatic selection environment
Evolution by natural selection
The dunes are a dramatic selection environment
Evolution by natural selection
Concealing coloration for predation avoidance
Color traits selected differently across variable landscapes
Natural selection: ruling out plasticity (w/ common gardens)
Natural selection: measuring selection in nature
Enclosure experiments
Natural selection: measuring selection in nature
Natural selection: measuring selection in genome
Natural selection: measuring selection in genome
Natural selection: apply findings across species
